How much does it cost to build a garage with an apartment above it in Saint John NB?

Building a garage with an apartment above in Saint John typically costs $120,000-$200,000 depending on size, finishes, and complexity. This represents one of the most substantial residential construction projects you can undertake, essentially combining a full garage build with a complete apartment construction above it.

The cost breaks down into two major components: the garage structure below and the apartment above. For the garage portion alone, expect $45,000-$70,000 for a standard two-car garage (24x28 feet) with the heavy-duty foundation and structural framing required to support living space above. This includes frost walls extending 4-5 feet below grade (essential in Saint John's climate), engineered floor joists rated for residential live loads, and a concrete slab with proper vapour barrier and drainage.

The apartment construction adds $75,000-$130,000 depending on size and finish level. A typical 600-800 square foot apartment above a two-car garage includes framing, insulation, drywall, flooring, kitchen, bathroom, electrical panel and circuits, plumbing rough-in and fixtures, HVAC system, windows, exterior doors, and interior finishing. Higher-end finishes, larger square footage, or complex layouts push costs toward the upper range.

Saint John's Maritime climate significantly impacts this project. The structure must handle snow loads of 2.4-3.2 kPa, persistent coastal winds, and high humidity year-round. Proper insulation and vapour barriers are critical — the apartment will be heated year-round while the garage below may be unheated, creating potential condensation issues without proper design. The foundation must extend below Saint John's 4-foot frost line, and the building envelope requires careful attention to air sealing and moisture management given the Bay of Fundy's influence on local humidity.

Permitting and code compliance add complexity and cost. This project requires building permits from the City of Saint John, and the apartment portion must meet full residential building code requirements including egress windows, smoke detectors, proper ceiling heights (minimum 7.5 feet), and potentially sprinkler systems depending on size. If you plan to rent the apartment, additional requirements for secondary suites may apply, including separate electrical meters, independent HVAC systems, and sound insulation between units.

The structural engineering is more complex than a standard garage. Floor joists must carry residential live loads (40 pounds per square foot minimum), and the garage ceiling becomes the apartment floor system. This typically requires 2x10 or 2x12 joists on 16-inch centers, or engineered I-joists for longer spans. The garage walls below must be designed to carry the additional load, often requiring 2x6 framing instead of standard 2x4 garage construction.

Electrical and plumbing rough-in must be planned carefully. The apartment requires its own electrical panel (or large sub-panel), dedicated circuits for kitchen appliances, bathroom GFCI outlets, heating system, and potentially separate metering if it will be rented. Plumbing involves running supply and drain lines from the main house or municipal connections, including proper venting through the roof. In Saint John's cold climate, any plumbing in exterior walls requires careful insulation and heating to prevent freezing.

Timing and seasonal considerations matter significantly. Foundation work should be completed between April and November when ground conditions allow proper excavation and concrete curing. The structural work can continue into winter, but exterior envelope completion (roofing, siding, windows) should ideally finish before sustained freezing temperatures arrive. Interior finishing can proceed year-round once the building is weathertight.

When to hire professionals: This project requires professional design and construction throughout. Foundation work, structural framing, electrical, plumbing, and HVAC all need licensed trades and inspections. The complexity of supporting living space above a garage, combined with NB's frost depth and snow load requirements, makes this unsuitable for DIY construction. However, you can save $15,000-$25,000 by handling interior painting, some flooring installation, and finish carpentry yourself.

Consider the ongoing costs: A heated apartment above an unheated garage creates thermal bridging and higher heating costs. Many homeowners choose to insulate and heat the garage as well, adding $3,000-$6,000 to the project but improving overall energy efficiency and preventing frozen pipes in the apartment above.

Need help finding a professional garage and apartment builder? New Brunswick Garages can match you with experienced contractors through the New Brunswick Construction Network who specialize in these complex residential projects.